Enabling ultrahigh rate and capacity sodium metal anodes with lightweight solid additives

Abstract Sodium (Na) metal is a promising anode for grid-scale energy storage systems owing to its high theoretical capacity and low cost. However, severe Na dendrite growth during cycling causes unsatisfied performance and safety concerns. Herein, extremely stable Na metal anodes with superior capacity and ultrahigh-rate capability are achieved by employing lightweight nitrogen (N)-doped graphene microcubes as solid additives. The direct addition of the as-obtained microcubes into bulk Na not only facilitates homogenous Na plating, but also minimizes volume change during cycling. Consequently, with only 3 wt% addition of N-doped graphene microcubes, an extremely stable Na metal anode can be realized in additive-free carbonate electrolytes at an ultrahigh current density of 20 mA cm−2 with an ultrahigh capacity of 10 mAh cm−2 over 250 h. Full cells based on the Na anodes with the assistance of solid additives exhibit significantly improved electrochemical performance in carbonate electrolytes. This work can provide a viable pathway towards the realization of high-energy Na battery systems.